Acid-Leached Rocks
As you walk along the creek flowing out from the bog, check out the rocks. Notice that the ones in the water are much darker than the other rocks in the area. Why are these rocks so dark? It actually has to do with the water chemistry of the kettle bog.
Donna Vogler explains: “When the waters are still and there’s not a lot of churning and movement, the waters become anaerobic (depleted of oxygen). The high levels of carbon dioxide makes the water acidic, and the more acidity, the more bog-like it becomes. Decaying plant material in the bog acts as a carbon sink, meaning the bog absorbs more CO2 than it releases.
Globally, peat bogs represent a significant carbon sink. Coal actually comes from peat, compressed in the earth over geological time frames. The peat bogs of Ireland the Great Britain have been used for thousands of years as a source of heat, releasing C02 back into the atmosphere.
Back to the black rocks you see in the creek. Their origins lie in the water of the kettle bog. The acidic water of the bog causes higher than normal amounts of metals like copper, aluminum and lead to be present in the water, and these metals have stained the rocks in the creek, darkening them.